#define TWIE 0
#define TWEN 2
#define TWSTO 4
#define TWSTA 5
#define TWEA 6
#define TWINT 7

#define START 0x08
#define R_START 0x10
#define MT_SLA_ACK 0x18
#define MT_SLA_NACK 0x20
#define MT_DATA_ACK 0x28
#define MR_SLA_ACK 0x40
#define MR_DATA_ACK 0x50
#define MR_DATA_NACK 0x58